The insulation itself is in fairly ragged shape after I pulled it down and then replaced it. (I wanted to avoid it getting soaked due to a plumbing leak above.)
In addition to being in poor shape, when I went to reinstall the light bulbs I'd removed when I pulled the insulation down I noticed that both appeared to have suffered damage from overheating, presumably due to being in direct contact with the insulation.
Am I safe in assuming the insulation was only needed originally because incandescent bulbs put out much larger quantities of heat, and that it is no longer needed with modern low power bulbs.